A known fixing device, for example, as disclosed in Japanese Laid-Open Patent Publication No. 2014-063003, includes a mechanism that varies pressure at a nip between a heat roller and a pressure roller, with a cam rotated by an operating lever. The cam is attached to a pressure arm that supports the pressure roller. More specifically, a surface of the cam contacts a support surface of a frame member that rotatably supports the heat roller. Rotation of the cam changes the position of the pressure arm, thereby varying the pressure at the nip. The surface of the cam and the support surface of the frame member are each non-stepped or flat in an axial direction of the cam.